The increasing demand for high-bandwidth mobile applications, such as, but not limited to, smart phones, tablets, wireless networks and the like, has created a need for high-frequency (e.g., about 500 MHz and above), relatively high-power (e.g., about 30 to 250 watt) devices, such as, but not limited to, power amplifiers.
High-frequency power amplifiers are dominated by devices based on wide bandgap material substrates, such as, for example, gallium arsenide (GaAs). One advantage of using GaAs as a substrate, as compared to silicon for example, is the inherently high carrier mobility and low parasitic capacitance, making it well-suited for high-frequency operation. However, aside from the increased cost of GaAs, one drawback for GaAs devices is that GaAs fabrication is generally not compatible with a traditional silicon fabrication process. Hole mobility in a GaAs process is lower compared to a silicon process, thereby resulting in lower performance P-channel GaAs devices relative to corresponding P-channel devices formed in silicon. Moreover, because GaAs has high impurity densities, it is difficult to fabricate small structures in a GaAs process. Consequently, integrating GaAs power transistors with other devices on the same die poses a significant challenge.